Input devices, including proximity sensor devices (e.g., touchpads or touch sensor devices), are widely used in a variety of electronic systems. A proximity sensor device may include a sensing region, often demarked by a surface, in which the proximity sensor device determines the presence, location and/or motion of one or more input objects. Proximity sensor devices may be used to provide interfaces for the electronic system. For example, proximity sensor devices may be used as input devices for larger computing systems (such as opaque touchpads integrated in, or peripheral to, notebook or desktop computers). Proximity sensor devices are also often used in smaller computing systems (such as touch screens integrated in cellular phones).
The detection of input objects in the sensing region is performed using sensor electrodes. The sensor electrodes are driven with sensing signals and capacitive measurements are acquired from the sensor electrodes. In some scenarios, the input device is in a low ground mass state. For example, the input device may be placed on an insulating surface and not have an electrical path to ground. When the input device is in a low ground mass state, detecting the presence of any input objects in the sensing region may be a challenge.